1. Field of the Invention
The present invention relates generally to a vacuum interrupter and in particular to an electrode for a vacuum circuit breaker having a coil for producing a magnetic field.
2. Description of the Related Art
A vacuum circuit breaker is an equipment disposed in a power receiving and distributing system and plays a role of disconnecting a specific portion from the power system when needed. In particular, the vacuum circuit breaker carries out the function of interrupting several thousands to several tens of thousands of amperes of current at the time of an accident.
A vacuum circuit breaker is adapted to make or interrupt a current by touching or detaching a pair of contact electrodes disposed inside a vacuum container with each other. It is widely known in the art that performance of interrupting a current improves by means of an applied magnetic field (hereinafter called the axial magnetic field) that is vertical to the end faces of the contact electrodes applied.
A structure in which a coil portion for producing a magnetic field is provided on the back of a contact electrode is widely adopted for such an electrode for a vacuum interrupter of an axial magnetic field type. An arc which is produced at the time of interrupting current is confined in a magnetic field to prevent the arc from locally heating the surface of the electrode, that is, to distribute a thermal load resulting from the arc to the overall surface of the electrode, such that the current interruption performance improves.
A vacuum interrupter provided with a coil electrode for producing a magnetic field is disclosed in JP-2008-135338-A. In the vacuum interrupter, a cylindrical conducting body is provided on its surface area with slits inclined with respect to the axial direction of the conducting body, thereby forming a coil portion for producing an axial magnetic field.